The proposed program emphasizes investigations in two areas. First, utilizing leads of some preliminary experiments, preparation of a series of hitherto unknown 7-cis geometric isomers of vitamin A1, vitamin A2 and the corresponding retinaldehydes, and 7-cis or 7, 7'- dicis isomers of carotene and related compounds will be attempted and their chemical and biological properties be examined. Secondly, the photochemistry of polyenes in general will be examined. Results are expected to contribute to general understanding of the physical and chemical excited state properties of this important class of natural occurring compounds, to assist finding conditions for synthetically useful photochemical processes and possibly to lead to preventive means against destructive photochemical processes in natural occurring polyenes.